Dissecting role of founder mutation p.V727M in GNE in Indian HIBM cohort

GNE gene-specific c.2179G>A(p.V727M) is a key alteration reported in patients with hereditary inclusion body myopathy (HIBM) and represents an ethnic founder mutation in the Indian cohort. However, the underlying role of this mutation in pathogenesis remains largely unknown. Thus, in this study, we aimed to access possible mechanisms of V727M mutation that could be leading to myopathy. We evaluated various in silico tools to predict the effect of this mutation on pathogenicity, structural or possible interactions, that could induce myopathy. Our results propose that V727M mutation could induce deleterious effects or pathogenicity and affect the stability of GNE protein. Analysis of differential genes reported in the V727 mutant case suggests that it can affect GNE protein interaction with Myc-proto-oncogene (MYC) transcription factor. Our in silico analysis also suggests a possible interaction between GNE ManNac-kinase domain with MYC protein at the C-terminal DNA-binding domain. MYC targets reported in skeletal muscles via ChIP-seq suggest that it plays a key role in regulating the expression of many genes reported differentially expressed in V727M-mutated HIBMs. We conclude that V727M mutation could alter the interaction of GNE with MYC thereby altering transcription of sialyltransferase and neuromuscular genes, thus understanding these effects could pave the way for developing effective therapies against HIBM.

Hereditary inclusion body myopathy: a clinical and genetic review

Introduction. Inclusion body myositis represents the most common acquired myopathy in clinical practice in patients over 50 years old. Despite classical approach to this myopathy as an inflammatory disorder, a muscle degenerative disorder is now considered the main mechanism linked to these vacuolar myopathies. Hereditary presentations, although quite rare, represent an expanding and underrecognized group in clinical practice. Objective. perform a structured review of the current literature regarding hereditary inclusion body myopathies. Method. review of U.S. NLM PubMed and MEDLINE database of original articles, case reports, case series and review articles including the terms “inclusion body myositis” OR “inclusion body myopathy” AND “genetics” OR “hereditary”. Results. We present in this article a wide review regarding the main clinical, imaging, pathophysiological, genetic and therapeutic aspects related to hereditary myopathies linked to seven different clinical and genetic presentations (GNE, MATR3, VCP, SQSTM1, MYH2, HNRNPA2B1 and HNRNPA1). Conclusion. Hereditary inclusion body myopathy is associated with at least 7 distinct clinic and genetic monogenic forms.

GNE Myopathy in Turkish Sisters with a Novel Homozygous Mutation

Background. Hereditary inclusion body myopathy is caused by biallelic defects in the GNE gene located on chromosome 9p13. It generally affects adults older than 20 years of age.Methods and Results. In this study, we present two Turkish sisters with progressive myopathy and describe a novel mutation in the GNE gene. Both sisters had slightly higher levels of creatine kinase (CK) and muscle weakness. The older sister presented at 38 years of age with an inability to climb steps, weakness, and a steppage gait. Her younger sister was 36 years old and had similar symptoms. The first symptoms of the disorder were seen when the sisters were 30 and 34 years old, respectively. The muscle biopsy showed primary myopathic features and presence of rimmed vacuoles. DNA analysis demonstrated the presence of previously unknown homozygous mutations [c.2152 G>A (p.A718T)] in the GNE genes.Conclusion. Based on our literature survey, we believe that ours is the first confirmed case of primary GNE myopathy with a novel missense mutation in Turkey. These patients illustrate that the muscle biopsy is still an important method for the differential diagnosis of vacuolar myopathies in that the detection of inclusions is required for the definitive diagnosis.